1. Field of the Invention
This invention relates to electronic circuits, and more particularly, to level shifter circuits.
2. Description of the Related Art
Many modern integrated circuits (ICs) utilize multiple operating voltages. Some circuits can operate better at lower voltages, while others may function better at higher voltages. Accordingly, many ICs may include multiple power domains, each of which includes circuitry that may operate based on an appropriate supply voltage. For example, an IC having multiple power domains may include one or more processor cores that operates at a voltage of 0.8 volts, and may include a memory that operates at 1.2 volts.
Despite the different operating voltages of circuits in different power domains, it may nevertheless remain necessary for such circuits to communicate with each other. For example, the processor cores of the exemplary IC noted above may need to write data to the memory and read data therefrom. Accordingly, such reads and writes may require the transmission of signals across boundaries between two power domains operating at different voltages.
To transfer signals across boundaries of power domains, level shifter circuits may be used. A level shifter may be a static logic circuit that receives signals at a first voltage corresponding to a supply voltage of a first power domain, and outputs signals at a second voltage corresponding to a supply voltage of the second power domain. Level shifters may be used for shifting a voltage up (when the voltage of the second domain is greater than the first) as well as down (when the voltage of the second domain is less than the first).